This invention relates to unsaturated polyester-polyurethane hybrid resin foam compositions. More specifically, this invention relates to improved water blown, thermosetting, unsaturated polyester-polyurethane hybrid resin foam compositions.
Polyester-polyurethane hybrid resins are well-known in the art of thermoset compositions. These resins are normally tougher than unsaturated polyesters and stronger, stiffer and less expensive than polyurethanes. Such hybrid resins usually comprise a hydroxy-terminated unsaturated polyester polyol, an ethylenically unsaturated monomer such as styrene and a polyisocyanate. Such resins are described in Edwards, 39th Annual Conference, Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., Jan. 26-29, 1984. They have been commercially available from Amoco Chemical Company under the trademark Xycon hybrid resins and supplied as two component systems having an A and a B side. The A side contains the polyisocyanate and a free radical initiator, while the B side contains the hydroxy-terminated unsaturated polyester polyol/styrene solution and optionally a peroxide promoter and a polyurethane catalyst and a filler.
Polyester resin foam compositions are described in U.S. Pat. No. 4,460,714, which discloses a low density polyester resin foam made from an admixture of an unsaturated polyester resin, an organic isocyanate compound, a blowing agent, a peroxide curing agent system, a surfactant, and small amounts of an inorganic iron salt. The use of an amine compound, as in the present invention, to impart nucleation sites to the foam composition is not disclosed.
The prior art, including U.S. Pat. Nos. 3,325,421; 4,310,448; 4,305,857; 4,184,990; 4,093,569; 4,092,275; 4,310,449; 4,496,678; 4,147,680; 4,305,858 and 4,523,025, teaches the preparation of dispersions of polyisocyanate polyaddition products in hydroxyl-containing compounds to form polyurea polyaddition products, polyurethane resins and foams. In all of these references, a nearly balanced NCO:NH ratio is disclosed, whereas the present invention uses about a 10:1 or greater ratio of NCO:NH to provide a rigid urea phase imparting nucleation sites for foaming within a polyesterpolyurethane hybrid phase.
U.S. Pat. No. 4.855,368 teaches the combination of a polyol, a polyisocyanate and an aromatic amine to prepare reaction injection molding compounds. The aromatic diamine is added to the polyol and then mixed with the polyisocyanate during molding, but no foam compositions are disclosed. U.S. Pat. No. 4,868,231 discloses sheet molding compounds that use aromatic diamines as thickening agents via "in situ" fermation of polyureas. There the molar ratio of isocyanate to amine is generally from about 0.6 to about 1.4 and, preferably, from about 0.8 to about 1.2 (Col. 7, lines 31-33).
In commonly assigned, co-pending U.S. patent application Ser. No. 575,069, incorporated by reference herein, solid molding compositions are disclosed having a soft polyurea phase within a more rigid polyesterpolyurethane hybrid phase. The soft polyurea phase enables improved impact and shrink control. The compositions taught therein are substantially water-free and no foam compositions are taught. Further, there is no disclosure of a rigid urea phase which imparts finely dispersed nucleation sites within a polyester-polyurethane hybrid foam composition, as taught herein.